Albany 2001

Biomolecular
Stereodynamics
SUNY at Albany
June 19-23, 2001

Dynamics of the interaction between L11 and EF-G during tRNA translocation

L11, a protein of the 50S ribosomal subunit known to be involved in the translocation process, is only partially visible in recent X-ray maps. Cryo-EM of a ÐL11 mutant and wild type shows both C-terminal domain and N-terminal domain (NTD) of the protein [1], enabling us to interpret two EF-G contacts in the stalk-base region of the ribosome [2,3] in atomic detail. One of these contacts is between domain V of EF-G and the cleft formed by the 23S rRNA and the NTD of L11, the other between domain G' of EF-G and the tip of the NTD of L11. The analysis of cryo-EM maps showing the EF-G-ribosome complex before [2] and after [2,3] GTP hydrolysis presents a picture of a complex dynamic process involving conformational changes in EF-G as well as the stalk base. One of the consequences of these changes is that domain V of EF-G intrudes into the before-mentioned cleft, forcing the NTD of L11 into a position more proximal to the GÕ domain. The other consequence is that the GÕ domain itself moves "upwards", toward forming a contact with the tip of the NTD. Thus, the "arc-like connection" observed in the post-GTP hydrolysis EF-G-ribosome complex [2,3] can be explained, and, by inference, a similar connection found earlier by Stark and coworkers [4] can be explained as an analogous mechanism, this time involving the G domain of EF-Tu. A tentative explanation of the role of the arc contact is that it might aid in the release of the elongation factors after all other contacts have been destabilized.

Howard Hughes Medical Institute(1), Health Research, Inc. at the Wadsworth Center(2), Empire State Plaza, Albany, New York 12201-0509
Department of Biomedical Sciences(3), State University of New York at Albany, Empire State Plaza, Albany, New York 12201-0509
Max-Planck-Institut f?r Moleculare Genetik(4), Ihnestrasse 73, 14195 Berlin, Germany